186 PRACTICAL HISTOLOGY [XXHI 



then be placed in 1 p.c. osmic acid ; or alcohol or mercuric 

 chloride may be -injected into the blood vessels. 



In summer and autumn, the cells are usually granular 

 throughout and have but few fat globules and little glycogen. 

 In winter and spring, the granules are usually confined to the 

 inner zone of the cells, the outer zone being chiefly glycogen ; the 

 fat globules may be either in the inner zone, or in the outer zone, 

 the latter is commonly the case in spring especially in unhealthy 

 frogs. Pigment masses, some looking like altered red corpuscles, 

 are present between the tubes. 



